yAniv-k said
Yes, I found some on Facebook and spotted one of my files printed in my town

Wow, I came across a similar instance a week back where I saw a Christmas poster replicated on a glass of an electronic store on my way to work. I found out the name of the company and sent an official polite email asking the reference to where did they buy the design from (The design was made for an in-house project at my company so no way it was for sale).

Well, they did not revert with a feedback so I made some calls via website info and boom they didn’t know as some freelance designer made that design for them. Now I’m following up with that. It being a long way around you can always politely email them asking reference to where did they buy the design from and confirming over the place whether it was sold to them. If not then following up with another email asking to see the receipt or invoice. And if they don’t have one then ask them for a compensation or take that up however you feel like. Just don’t go there & beat those chaps up